Applicare la formula: $\frac{a}{b}c$$=\frac{ca}{b}$, dove $a=-4$, $b=3$, $c=5$, $a/b=-\frac{4}{3}$ e $ca/b=5\cdot \left(-\frac{4}{3}\right)$

Applicare la formula: $ab$$=ab$, dove $ab=5\cdot -4$, $a=5$ e $b=-4$

Applicare la formula: $\frac{a}{b}+\frac{c}{b}$$=\frac{a+c}{b}$, dove $a=-20$, $b=3$ e $c=5$

Applicare la formula: $a+b$$=a+b$, dove $a=-20$, $b=5$ e $a+b=-20+5$

Applicare la formula: $\frac{a}{b}$$=\frac{a}{b}$, dove $a=-15$, $b=3$ e $a/b=-\frac{15}{3}$